1. NL12 Girder Removal and Reinstallation
Information provided by Danny Forehand and Greg Marble

2. Historical girder removal techniques
Girder and associated area are cleaned/wipe down with Isopropyl Alcohol for beam line and H2O for girder pedestal and tunnel floor.
Girder and associated area draped with cascading aluminum foil
Flow hood placed over the work area and taped into place
Technician dons head cover, clean room smock and gloves
Floor covered with aluminum foil
Another cleaned/wipe down with Isopropyl Alcohol and lint free wipes of connection/disconnection points (conflats)
Pump cart connected to girder to allow for N2 bleed-up. Pump cart is pumped and purged with 3 atmosphere He five times prior to opening girder right angle valve
Downstream and upstream cryomodules are isolated with the “warm” isolation valves
Warm isolation valve on opposite end of the cryomodule being removed are also closed
Girder being bled up is isolated from the cryomodule with cryomodule “warm” isolation valve
Girder is bled up with He through right angle isolation valve located at the “A” ion pump. He is supplied through .5 micron inline filter. He supplied from cryogenic 3 atmosphere system
Pump cart needle valve is cracked open to bleed up the girder.
Girder beam-line flanges are removed from the warm isolation valves
Blanks are installed on both the girder beam-line flange and the open “warm” isolation flange
Girder is pumped down to UHV levels. Pump cart is disconnected from girder right angle isolation valve.
Flow hood removed
Girder is placed off to the side until the replacement cryomodule arrives for installation
Repeat setup/procedure of flow hood and equipment at next girder to be removed.

3. Girder Removal for NL12
We set up on girder 1L13 first (upstream of NL12)
Greg did a really thorough cleaning of the entire girder--including the removal of external magnets and associated wiring
The surrounding floor area was mopped--including several feet under the end of the cryomodule
The entire girder was wrapped with clean room bagging material and taped off leaving only several inches of beam-line exposed
Greg built an addition to the flow hood adding a gowning area which was separate from the working area
Clean room bagging material was taped to the floor extending beyond the boundaries of the flow hood
The entire area inside the flow hoods were wiped with alcohol soaked lint free wipes
Sticky mat was placed outside the gowning area of the flow hoods
Technician used gowning area to don shoe covers, hair net, face mask, rubber gloves and clean room suit (in my opinion a smock would be sufficient for this operation)
Lighthouse particle counter was in use the during the entire operation
Particle counts inside the flow hood were zero before beginning operations
Wiped the externals of the right angle girder isolation valve located at ion pump

4. Removed aluminum foil from the open flange
Blew the internals of the valve (bellows on the stem side) with an ionized N2 gun connected to a nitrogen bottle (pressure of the local N2 was not sufficient for blowing off parts)
The ionized N2 spraying is done IAW the C50R Ionized Nitrogen Cleaning procedure (paying attention to the Cavity Components Cleaning paragraph) C50 Ionized Nitrogen Cleaning Procedure
Particle count data was monitored during this operation
The counts were quite high (1000’s at .3 microns) in the beginning but recovered quickly to an acceptable range .3microns
Connected the portable slow bleed up system (to be covered later by Ari)
Valve alignment was as follows: Cold isolation valves on NL11-8, NL12-1 & 8, NL13-1 and all cryomodule warm isolation valves were closed. Warm isolation valves at and around NL12 are known to leak through.
Started the bleed up of the girder and cryomodule with a goal of less than 10mbar per minute. *The procedure for slow bleed up is still in development .
Ion pump activity was being monitored on the upstream girder (VIP1L12A) and downstream cryomodule (VIP1L13B) while the bleed-up was progressing
The ion pump activity indicated to us that cryomodule cold valve CV1L12-8 was leaking by. We immediately closed 1L12-7 and a few minutes later we had to close 1L12-6.
We also had to open VBV1L13B and read vacuum pressure at VIP1L14A
We lost communication with ion pump readout. After re-establishing we noticed a fault on VIP1L12B. Tried to restart with no success. Continued slow bleed up of girder 1L13 until it reached atmosphere. Secured system for the night

5. Upon returning in the morning we found the pressure in girder 1L13 was lower than atmosphere due to valves leaking through to cryomodule NL12
Verified that the pressure for both NL11 and NL13 were stable ( 8 & 9 range)
Contacted M. Drury and discussed opening all valves associated with NL12 with the exception CV1L12-8 to equalize pressure in girder 1L12, cryomodule NL12, and girder 1L13
System equalized at 140 torr. Opened CV1L12-8
Continued bleed-up at a rate of <5 torr/min until everything reached atmosphere
Wiped the flange and exposed pipe with alcohol soak rag
Removed four bolts from the flange VBV1L12B
Started spraying with ionized N2 while monitoring particle counts. Counts were as high as .3 microns and sprayed for approximately 15 minutes to reach counts below 25
Removed the last two bolts and placed a conflat blank on the valve.
Placed a conflat blank on the girder flange.
Repeated for the other side
Broke down the flow hood and started the procedure again on girder 1L12
Both girders were sent for further disassembly by the vacuum group
The beam-line components were completely dis-assembled in the clean room and samples were gathered
All the parts were cleaned by the chem techs and sent back into the clean room for re-assembly
After successful re-assembly and leak check, the sub-assembly was sent back to the vacuum group for installation back onto girder

6. NL12 Girder ready for removal

7. Beam-line components from girder 1L12
This pic was taken prior to dis-assembly and sample gathering

8. Girder Reinstallation for NL12
The area around girder 1L13 was set up in the same manner as during girder removal
The flow hoods were wiped with alcohol soaked lint free rags
Technician donned the clean room garments in the same fashion
Particle counts were monitored during the entire process
Four bolts were removed from the blank on the warm cryomodule isolation valve
Bolt holes were sprayed with ionized N2. Particle counts were monitored during this operation. The counts were not nearly as high as they were during the removal due to the fact they were just recently cleaned and sprayed
Counts started in the the .3 micron size and came down to less than ten rather quickly
Blank flange was removed from the gate valve
Internals of the closed gate valve were sprayed with ionized N2
The external surfaces of the girder bellows flange was wiped with an alcohol soaked rag
Blank was removed from the bellows flange on the girder.
Replaced the conflat gasket and carefully made the mechanical connection using clean vacuum practices This procedure was repeated on the other side of the girder and then again on girder 1L12

9. A slow pump down by-pass was installed on the pump cart
A slow pump down by-pass was installed on the pump cart. This is basically a metered needle valve that is plumbed in around the foreline valve on the turbopump.
The valve is opened 2.5 microns, allowing the system the be roughed down at a much slower rate (<10mbar/min).
The foreline valve can be fully opened at <20mbar and turbo started below 2mbar
Although the setup might be slightly different than outlined, the basic slow pump down procedure is followed for all slow pumping Standard Slow Pump Down Procedure

10. Recommendations
Continue the use of the two room flow hood that was built during this exercise
At a minimum add the use of facemasks to the appropriate garments for clean assembly work
Stop using aluminum foil as a cover for the girders and floor—although it can be wiped clean, aluminum is a terrible particle generator
Static free clean room bagging material is a good option
Always use a blank flange to cover open flanges—many flanges in the Linac only have aluminum foil over open flanges on the isolation valves
Keep the blank flange tight and tape over the gap between flanges
Always spray any flange being disassembled with ionized N2 after a majority of its bolts have been removed
Use a live time particle counter to monitor this activity ensuring that the flange is properly sprayed
Use the same ionized N2 spraying techniques to the internals on any closed valves that are having something attached
Always use a slow bleed-up and slow pump-down system when evacuating or venting beam-line components